The broad, long-term objective of this research program is to resolve certain questions concerning the causes of spontaneous mutations and genetic variations in mammals. In particular, the role of the Intracisternal A Particle (IAP) DNA element in the origin and reversion of the pink unstable, Pun, allele of the mouse pink-eyed dilute locus will be investigated. The proposed research is based on preliminary results that show a specific association of an IAP DNA element with the Pun genotype. The specific aims are to determine the molecular cause of the Pun mutation, uncover its mechanism of reversion, and characterize the wild type gene, P. The experimental design involves the isolation and determination of the DNA sequence in the region of the mutant-specific DNA fragment in three genotypes: Pun, wild-type and revertant. The P encoding sequences will also be determined. Standard molecular biological techniques will be employed in the molecular genetic analysis of this locus. This research has several implications for human health: 1) there are related retrovirus DNA elements in human DNA (M. Ono, J. Virol. 58:937, 1986) that may also contribute to human spontaneous mutations; 2) the isolation of the P gene will increase our knowledge of the molecular biology of melanocytes, the transformation of which to melanomas constitute a significant human health hazard; 3) the molecular genetic analysis of another allele of this locus, pink cleft palate or Pcp, may lead to the isolation of a gene mediating cleft palate formation in mouse that may have a human homologue; and 4) the isolation of mutant homologues of other genes that are similarly associated with IAP DNA elements will be facilitated, some of which may have a direct bearing on human health.